- Patients undergo surgical resection of intra-abdominal masses, if feasible. Patients with low-risk disease (completely resected tumor or a single extra-abdominal site of involvement (other than the mediastinum), but without lymphoblastic lymphoma) are assigned to treatment group 2. All other patients, including those with lymphoblastic lymphoma without bone marrow involvement, are considered high risk and they are assigned to treatment group 1.